There is known a method called an aerosol deposition method in which a structure made of a brittle material is formed on a surface of a substrate without undergoing a heating process. In this aerosol deposition method, aerosol, in which fine particles of a brittle material are dispersed in gas, is ejected from a nozzle toward a substrate such as metal, glass or ceramic so as to cause the fine particles to collide with the substrate. The fine particles of a brittle material are deformed or fractured by the impact of the collision so that the fine particles are joined with each other, and a structure made of the material of the fine particles is directly formed on the substrate. In particular, according to this method, it is possible to form such a structure at normal temperature without a heating means. Since the film structure formed by the aerosol deposition method has similar compactness to a sintered structure, which means that a film structure having high density and high strength can be provided (Patent Document 1).
Also, Patent Documents 2-5 describe a structure of yttrium oxide formed by an aerosol deposition method.    Patent Document 1: Japanese Patent No. 3265481    Patent Document 2: Japanese. Patent Application Publication No. 2005-158933    Patent Document 3: Japanese Patent Application Publication No. 2005-217349    Patent Document 4: Japanese Patent Application Publication No. 2005-217350    Patent Document 5: Japanese Patent Application Publication No. 2005-217351